The invention relates to antenna-gain diversity. Antenna-gain diversity is the provision of at least two different antenna patterns.
U.S. Pat. No. 5,548,837 describes a receiver that includes a first and second antenna element being characterized by a first and second antenna pattern, respectively. Together, the first and second antenna pattern produce a composite antenna pattern. To provide diversity gain of a signal received, the following is proposed. Each of the signals received by the first and second antenna element, respectively, is adjusted in amplitude. The amplitude-adjusted signals are combined, such that the composite antenna pattern is effectively rotated.
It is an object of the invention to provide antenna-gain diversity which is better suited for an application which needs to be relatively small in size or relatively inexpensive, or both.
The invention takes the following aspects into consideration. An antenna element which provides gain in one or more specific directions is relatively spacious and costly. The background-art technique of antenna-gain diversity requires two such antenna elements. Consequently, the background-art technique of antenna-gain diversity will not be suited for low-cost applications, for example, in the field of consumer electronics. The background art technique will also not be suited for small-size applications such as, for example, cordless telephones.
In accordance with the invention, a first and a second antenna element are electro-magnetically coupled, and a switchable antenna-coupler is switchable between:
a first antenna-coupling state in which the first and the second antenna element are electrically coupled to an antenna-signal node; and
a second antenna-coupling state in which the first antenna element is electrically coupled to the antenna-signal node and the second antenna element is electrically coupled to signal ground.
In the invention, a different antenna pattern is obtained for each antenna-coupling state. To this effect, it is not necessary that the antenna elements provide gain in one or more specific directions. For example, in the invention, the antenna elements may have an omni-directional diagram. An omni-directional antenna element is relatively small and can be manufactured at relatively low cost. Since, in the invention, omni-directional antenna elements can be used, whereas this is not possible in the background art, antenna-gain diversity in accordance with the invention is better suited for an application which needs to be relatively small in size or relatively inexpensive, or both, such as a cordless telephone, for example.
Another advantage of the invention relates to the following aspect. In the invention, the switchable antenna-coupler switches between two antenna-coupling states, whereas in the background art, an antenna coupler carries out amplitude adjustments. Switching is a relatively simple function, whereas adjusting amplitudes is a relatively complicated function. An antenna coupler will generally have better signal-handling properties if it carries out a relatively simple function than if it carries out a relatively complicated function. Consequently, the switchable antenna coupler, which is used in the invention, will generally have better signal-handling properties than the antenna coupler which is used in the background art. In a wireless-communication apparatus, which comprises an antenna coupler, the signal-handling properties of the antenna coupler substantially influence one or more performance aspects of the wireless-communication apparatus. Consequently, the invention allows a wireless-communication apparatus having a better performance as compared to the background art.